Warning: SPOILERS for Riverdale's season 2 premiere ahead
Riverdale is a town full of drama - from the shady Southside Serpents to the strange goings-on up at the Blossom family home Thornhill - but in season 1 Archie Andrews had perhaps the most "normal" problems out of the gang. A disturbing relationship with his music tutor Ms. Grundy got him into writing music, which led him to working with Josie and the Pussycats, which led to more relationship drama... all while Riverdale was gripped by a horrifying murder and the mystery of who the killer was.
In season 2, however, Archie is at ground zero for the show's big mystery, following the dramatic season 1 finale in which a hooded gunman held up Pop's Chock'lit Shoppe and shot Fred Andrews in the stomach. Archie's dad thankfully survived the injury, but Ms. Grundy wasn't so fortunate. After being absent from the show for much of season 1, Grundy returned in "A Kiss Before Dying" briefly, only to be killed off by the hooded man as a shocking final stinger for the episode.
The question now, of course, is who the man in the black hood is, and why he targeted Fred Andrews and Geraldine Grundy specifically. Let's break down what we know so far.
Here's what we know about the man under the hood: he's Caucasian, approximately five foot ten and 160lbs, appears to be in his 40s or 50s, and has green eyes. He did not steal any money from Pop Tate, and interestingly he chose not to kill Archie even though he very easily could have. However, at some point between the shooting and Veronica emptying the bag of Fred's belongings from the hospital, Fred's wallet disappeared. The same killer (or is it?) later goes to Greendale and murders Ms. Grundy after she finishes a lesson with her new student/victim.
First, let's address the eyes: the detail that Archie remembers best, and therefore the detail most likely designed to mislead Riverdale's audience. The existence of colored contact lenses means that we cannot write off any characters for not having the right eye color - in fact, the shooter may have deliberately allowed witnesses to get a good look at his eyes in order to ensure that the police would be looking for a green-eyed man.
Second, let's look at the victims so far. Fred Andrews was involved with a married woman, and Ms. Grundy was a statutory rapist who had exhibited a pattern of grooming minors in her charge, so the killer may have been motivated by moral outrage. Both victims also had a connection to Archie - his father, and his former lover. We know from season 1 that Geraldine Grundy's real name is Jennifer Gibson, and she told Archie that she had an abusive ex-husband who beat her so badly that she ended up in the ER with multiple broken bones.
With all that in mind, let's try and figure out who the man under the black hood might be.
The current popular choice among fans, Hal fits the physical description, save for the fact that he has blue eyes instead of green, and what we can see of the killer's face looks a lot like Lochlyn Munro. He's also demonstrated in the past that he has a dark side - pushing his wife Alice to get an abortion (she gave the baby up for adoption instead), doing the same to his daughter Polly when she became pregnant, and then sending Polly to the Sisters of Quiet Mercy, effectively turning her into a prisoner. He was suspected of being Jason Blossom's killer in season 1, and while he was ultimately proven innocent, there is something about Hal that's just not quite right.
The main snag here is that Hal Cooper has no motive, that we know of, for hating Fred Andrews or Geraldine Grundy, though he does have a deep-seated hatred of the Blossom family. However, Riverdale is a town full of secrets, and it wouldn't be surprising if Hal had his own reasons for shooting Fred and killing Grundy.
If you're looking around Riverdale for a middle-aged man of average height and build with green eyes, look no further than Sheriff Keller, father of Archie's friend Kevin Keller. Now, there isn't much in the way of motive connecting the Sheriff to either of the victims, but he was at the hospital after Fred was shot and could conceivably have stolen his wallet. He was also very quick to round up suspects for Archie to point the finger at, though Archie could not find his father's would-be killer among the crowd.
As the head of Riverdale's police department, Sheriff Keller is ideally positioned to sabotage the investigation, and is also close enough to the show's main friendship group that he could spy on them and always stay one step ahead. If Sheriff Keller is the killer, then Archie and his friends are going to have a tough time figuring it out.